A pilot scheme to test mobile phone signal blocking technology in Scottish prisons will go live in two jails in the next few weeks, Justice Secretary Kenny MacAskill announced.

MacAskill was visiting HMP Shotts, one of the prisons chosen for the pilot, to see the technology beings installed and said that the scheme was due to get the green light within weeks. The other prison in the trial is HMP Glenochil.

Mobiles are banned in prisons as there are fears that although some prisoners may be using their mobes to stay in touch with family and friends, other phones are being used to conduct criminal activities. Mobile use has been linked to gang activity and organised crime as well as victim harassment and drug supply into prisons.

Scotland already introduced legislation that allowed prison staff to interfere with the wireless signal in their jails in order to stop prisoners from being able to communicate with the outside world.

"This government made it a criminal offence for a prisoner to possess a mobile phone and the Scottish Prison Service has already invested considerably in the use of technology and intelligence capability to detect and prevent the use of mobile phones in our prisons," the justice secretary said.

"This new legislation will allow SPS to further extend their technology to disrupt the use of mobile phones by prisoners and is scheduled to be operational in a matter of weeks."

Prisons in the rest of Blighty may have to wait some time for similar jamming technology, as the Ministry of Justice has claimed that signal blocking in all jails would be "prohibitively expensive".